The big picture

13th July 2001 at 01:00
(Photograph) - What's the story? It was one of the more upsetting news stories of recent weeks - the revelation that each year a tract of Indonesian rainforest the size of Belgium is being pulped to provide cheap paper products such as kitchen roll and fax paper.

But an equally telling illustration of what we stand to lose by indiscriminate logging might have been this stunning photograph of a coral reef. For as surely as loggers kill trees, so they also kill coral, in ways which we are only just beginning to understand.

Coral reefs are frequently described as the submarine equivalent of rainforests, and the comparison is far from fanciful. For these vast structures - the Great Barrier Reef off the north-east coast of Australia is 100 miles wide and more than 1,000 miles long - are home to more than a million species of plants, animals and microbes.

Like a rainforest, a reef comprises many micro-environments, and so intricate are their connections that damage to one can quickly destabilise the entire system.

Algae living on the surface of a reef, for example, need sunlight. But clear-felling of forests leads to soil erosion, and when rivers cloud the sea with sediment, the sun-starved algae - and the corals with which they live in symbiosis - perish.

Tree felling is invariably accompanied by burning, and it is the products of burning - notably carbon dioxide - that carry on the destruction.

When carbon dioxide accumulates in the atmosphere, the planet heats up, and as coral thrives only at certain temperatures, much of its current decline is attributed to global warming.

Increases of only one or two degrees can "stress" the corals - invertebrate marine organisms the external skeletons of which form the framework of a reef. When stressed, these tiny creatures eject the colourful algae that live in their stomachs, and it is this that leads to the "bleaching" of unhealthy colonies.

But scientists from the National Center for Atmospheric Research in the United States recently discovered another way in which carbon dioxide can destroy reefs.

Carbon dioxide in the atmosphere dissolves in seawater to form a mild acid, and ocean acidity rises when the air contains more of the gas. By creating an artificial ocean in a three-acre, glass-enclosed biosphere in Arizona, researchers showed that excess acid interferes with the complex process by which coral organisms secrete calcium carbonate, causing a reef to stop growing.

And that could just be the start of a vicious circle. Because in the same way as a forest absorbs carbon dioxide, so a healthy coral reef draws it from the atmosphere, converting it into stone. By killing coral, we destroy not only a thing of beauty, but also a part of the mechanism that keeps the planet habitable for oxygen breathers.

It's an exorbitant price to pay for cheaper kitchen roll. DAVID NEWNHAM

Weblinks. Oceanworld at http:oceanworld.tamu.edu has information for teachers and students on a wide range of ocean topics, including coral reefs.

To see how carbon dioxide slows coral growth visit Columbia Earth Institute at www.earthinstitute. columbia.edunews and search for coral.

Keep an eye on the corals at the Fisheye View labs in Coral Gables, Florida, by visiting Fisheye View Cam at www.FisheyeView.com.

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